Table of Contents
Advertisement
POWE R REQU I RE MENTS, GENE RAL
All d evices o perated on alternating cu rrent { AC} a re affected b y freq u e n cy.
si n u soidal w avefo rm can b e analyzed as a fundamental freq u ency pl us h a rm o n ics of that
fu n d a mental freq u ency. AC rel ays { a nd AC d evices i n general) a re si g n ificantl y affected b y
the a p pl i cation of non- si n u so i d al w avefo rms.
p ro pe rl y it is essential to use a test voltage and/or cu rrent w aveform that is sin uso idal. The
p u rity of the si ne w ave { i. e., its freed om from h a rmonics) ca n n ot be ex p ressed as a f i n ite
n u mb e r for any p a rticul a r rel a y; how ever, a ny rel ay usi n g t u n ed ci rcu i ts, RL or R C
n etw o rk s, o r satu rati n g el ectro m a g n ets {such a s t i m e- ove rcu rrent rel ays) w o ul d b e
essentiall y affected b y non-sin usoidal w aveforms. H e nce a resista nce-l i m ited ci rcu it , as
show n in Fig u res 1 1- 1 3, is reco m mended.
TI ME- OVE RCU R RENT UN IT
Rotate the time d i al sl owl y and check , by means of a l a m p, that the contacts j ust cl ose at
(O)
the z e ro
time- d i al sett i n g.
The point at w h ich the contacts j ust cl ose can b e adj usted b y ru n n i n g the statio n a ry
contact b rush i n o r out b y means of its adj usti ng screw.
W ith the contacts j ust cl osi ng at the z e ro (0) time setting, there shoul d b e sufficient g a p
b etw een the stationary- contact b rush a n d its metal b ack i n g stri p to ensu re a p p rox i matel y
1/ 3 2- i nch w i pe.
The m i n i m u m cu rrent at w h ich the contacts w ill j ust cl ose is d etermi ned b y the ta p sett i n g
i n the ta p bl ock at the top of the su pport structu re. See
The p i ck u p of the ti me- ove rcu rrent u n it for any cu rrent-tap setting is adj usted b y means of
a spri n g- adj usti ng ring (see Fig u re 1). The spri ng- adj usti ng ri n g either w i nds o r u n w i nds
the spi ral control spri n g. B y turn i n g the ring, the operati ng cu rrent of the u n it may b e
b roug ht i nto ag reement w ith the ta p setting empl oyed, i f this adj ustment h a s b ee n
d istu rb ed. Th is adj ustment al so perm its a n y desi red sett i n g i ntermed iate b etw een the
various ta p sett i ngs to b e obta i n ed. If such adj ustment is req u i red, it is recom mended that
the h i g h e r tap be used. It should be
the ti me- cu rrent cha racteristics of Fig u res 5 and 6 if the rel ay h as b een adj usted to p i ck up
at a val ue other th an ta p val u e, b eca use the torq ue l evel of the rel ay w ill have changed.
T i m e Sett i ng
The setting of the ti me d i al determ i n es the l ength of time that the u n it req u i res to cl ose
the contacts'w h e n the cu rrent reaches a pred et ermi ned val ue. The contacts a re j ust cl osed
w he n the time d i al is set on zero (0). W hen the time d i al is set on 1 0, the d isk m u st travel
the max i mu m a m o u nt to close the contacts and therefore this setting g ives the m ax i m u m
time setting.
The pri m a ry adj ustment for the time of operati o n of the u n it is made b y means of t h e time
d ial. H ow ever, fu rther adj ustment is obta i n ed b y movi n g the perm a n e nt mag n et al o n g its
su pporti n g shel f; movi ng the magnet tow a rd the d isk and shaft d ecreases the time, wh il e
movi n g it aw ay i n creases the time.
Set the rel ay at the 0.5 time- d ial positi on and the l ow est ta p. W ith the test con n ecti ons as
i n Fig u re 1 1 , the m a i n u n it shoul d cl ose the contacts w ith i n
GEK-49950
T h e refo re, i n o rd e r t o test A C rel ays
CHARACTERISTICS
noted
1 1
section.
necessa ril y a g ree w ith
not
±
3% of ta p- val u e cu rrent.
A n o n
Advertisement
Table of Contents
